A battery generates electric energy by oxidation and reduction reactions and is widely used in various ways. For example, a battery is applied to portable devices such as cellular phones, laptops, digital cameras, video cameras, tablet computers, and electric tools; electric-driven apparatuses such as electric bikes, motor cycles, electric vehicles, hybrid vehicles, electric ships, and electric airplanes; power storage devices used for storing power generated by new regeneration energy or surplus energy; uninterrupted power supplies for stably supplying power to various information communication devices such as server computers and base stations for communication, and so on.
A battery includes three basic components: an anode containing material which is oxidized while emitting electrons during discharge, a cathode containing material which is reduced while accepting electrons during discharge, and an electrolyte allowing the transfer of operating ions between the anode and the cathode.
Batteries may be classified into primary batteries which are not reusable after discharge, and secondary batteries which allow repeated charge and discharge since their electrochemical reaction is at least partially reversible.
The secondary batteries include lead-acid batteries, nickel-cadmium batteries, nickel-zinc batteries, nickel-iron batteries, silver oxide batteries, nickel metal hydride batteries, zinc-manganese oxide batteries, zinc-bromide batteries, metal-air batteries, lithium secondary batteries and so on, as well known in the art. Among them, lithium secondary batteries are drawing the most attention due to their high energy density, high battery voltage and long life cycle in comparison to other secondary batteries.
The lithium secondary battery has a distinctive feature in that intercalating and deintercalating reactions of lithium ions occur at a cathode and an anode, respectively. In other words, during discharge, lithium ions are deintercalated from the anode material included in the anode, transferred to the cathode through an electrolyte, and intercalated into the cathode material included in the cathode. During charging, the above processes are performed in reverse order.
In the lithium secondary battery, since the material used as the cathode material greatly influences the performance of the secondary battery, various attempts are being made to provide cathode materials having low production costs and large energy capacity while maintaining high-temperature stability.